ORLANDO. Responding to a competitor’s claims of aerodynamic superiority for a Class 8 tractor, International Truck and Engine Co. says independently conducted tests show its new ProStar is 5.7% more fuel efficient than the Freightliner Cascadia. The advantage, the company says, is the result of better aerodynamics and lower overall drag for its newest tractor design.
In September, Freightliner released wind test results that gave its new Cascadia a substantial aerodynamic edge over the ProStar, and therefore a corresponding fuel economy advantage. The tests were conducted at the company’s dedicated heavy-truck wind tunnel facility in Portland, OR.
International has answered by conducting SAE Type III fuel economy tests at the Goodyear Proving Grounds with two production trucks built for and provided by Wal-Mart. Both the ProStar and Cascadia were high-rise sleeper configurations with identical drivetrains, tires, trailer gaps and gross weights. The only difference was in the engines, with the ProStar using a Cummins ISX 400 ST rated at 400 hp. and the Cascadia a DDC Series 60 rated at 455 hp.
To meet the SAE standards for the Type III fuel economy tests, each truck had to complete a minimum of six runs with GPS used to confirm that both ran at a steady 65 mph. Both drivers and trailers were swapped during the tests to eliminate their impact, while tire pressures were monitored to ensure no variations. Fuel consumption was measured by weighing the fuel tanks. A second set of tests were run the next day to verify the initial findings within a 2% margin.
The result was a 5.7% average fuel economy advantage for the ProStar over the two days, according to Steve Gilligan, International asst. gm, heavy vehicle center. The published results “are conservative,” Gilligan said at a press conference during the American Trucking Assns.’ annual convention here. For example, fuel consumed during engine regeneration cycles by the 2007-spec Series 60 was not included in the fuel economy calculations, nor were test runs in winds over 15 mph which showed even larger fuel economy advantages for the ProStar, he said.
In a written response to International’s test announcement, Michael Delaney, sr. vp of marketing for Freightliner LLC, said: “We welcome head-to-head comparisons, and have done many of our own to assess the specific impact of cab, engine, driver and the dozens of other variables that affect fuel economy. Thus, we find Navistar's claims of a 5.7% fuel economy advantage to be highly misleading and potentially questionable information for customers making choices for normal, day-to-day operation.”
With International’s proprietary MaxxForce Big Bore diesel engine due to begin limited production in January, International says it plans to conduct further SAE Type III tests with the new powerplant, as well as over-the-road SAE Type IV fuel economy tests in the near future.
Full test results are available from International Truck and Engine Co.